The coefficient of x4 in (x2−3x2)10 is:
405/256
504/259
450/263
None
Tr+1=10Cr(x2)10−r(−3x2)r
Equating power of x to 4
10 - 3r = 4 ⇒ r = 2
So coefficient of x4 is 10C2(12)8(−3)2